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Direction Selectivity In Primary Visual Cortex Using Massive Intracortical Connections

Suarez, Humbert and Koch, Christof and Douglas, Rodney (1995) Direction Selectivity In Primary Visual Cortex Using Massive Intracortical Connections. In: Advances in Neural Information Processing Systems 7. The MIT Press , Cambridge, MA, pp. 3-10. ISBN 0-262-20104-6.

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Almost all models of orientation and direction selectivity in visual cortex are based on feedforward connection schemes, where geniculate input provides all excitation to both pyramidal and inhibitory neurons. The latter neurons then suppress the response of the former for non-optimal stimuli. However, anatomical studies show that up to 90 % of the excitatory synaptic input onto any cortical cell is provided by other cortical cells. The massive excitatory feedback nature of cortical circuits is embedded in the canonical microcircuit of Douglas &. Martin (1991). We here investigate analytically and through biologically realistic simulations the functioning of a detailed model of this circuitry, operating in a hysteretic mode. In the model, weak geniculate input is dramatically amplified by intracortical excitation, while inhibition has a dual role: (i) to prevent the early geniculate-induced excitation in the null direction and (ii) to restrain excitation and ensure that the neurons fire only when the stimulus is in their receptive-field. Among the cortical function, paralleling proposals for short-term memory, and strong limitations on linearity tests that use gratings. Properties of visual cortical neurons are compared in detail to this model and to a classical model of direction selectivity that does not include excitatory corti co-cortical connections. The model explain a number of puzzling features of direction-selective simple cells, including the small somatic input conductance changes that have been measured experimentally during stimulation in the null direction. The model also allows us to understand why the velocity-response curve of area 17 neurons is different from that of their LG N afferents, and the origin of expansive and compressive nonlinearities in the contrast-response curve of striate cortical neurons.

Item Type:Book Section
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Koch, Christof0000-0001-6482-8067
Additional Information:© 1995 Massachusetts Institute of Technology. This research was supported by the Office of Naval Research, the National Science Foundation, the National Eye Institute, and the McDonnell Foundation.
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Office of Naval Research (ONR)UNSPECIFIED
National Eye InstituteUNSPECIFIED
McDonnell FoundationUNSPECIFIED
Record Number:CaltechAUTHORS:20150305-151414592
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:55556
Deposited On:06 Mar 2015 05:35
Last Modified:03 Mar 2020 13:01

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